refactor: implement component-based architecture for enhanced maintainability

- Reorganize directory structure into core/, features/, and themes/
- Colocate application Nix logic, configs, scripts, and theme overrides
- Implement 'Inversion of Control' for theming: apps now pull theme-specific layouts
- Update flake.nix and shared library paths to match the new structure
- Document the new Feature-Centric architecture in README.md

TODO.md

@@ -3,18 +3,18 @@
 ## 1. Professional Installer [IN PROGRESS]
 - [x] Refactor with `gum` for stylized UI.
 - [x] Add clear section headers and environment checks.
-- [x] Implement software profile selection.
-- [ ] Add "Pre-flight Check" summary screen showing all selected options (disk, user, profiles) before proceeding.
-- [ ] Implement post-install "Success" dashboard with next steps.
+- [ ] Implement software profile selection.
+- [x] Add "Pre-flight Check" summary screen showing all selected options (disk, user, profiles) before proceeding.
+- [x] Implement post-install "Success" dashboard with next steps.
 - [ ] Improve disk selection to show more metadata (vendor, model, serial).
 
-## 2. Nomarchy Plymouth Theme [IN PROGRESS]
+## 2. Nomarchy Plymouth Theme [DONE]
 - [x] Create custom theme assets in `assets/plymouth/`.
 - [x] Center official logo on splash screen.
 - [x] Declarative integration in `modules/system/plymouth.nix`.
 - [x] Implement full LUKS password entry support (password prompt, bullet indicators).
 - [x] Add smooth fade-in/fade-out animations for the logo.
-- [ ] Add system message display (e.g., "Rebooting...", "Checking Disk...").
+- [x] Add system message display (e.g., "Rebooting...", "Checking Disk...").
 
 ## 3. System Branding (Fastfetch & Terminal) [DONE]
 - [x] Restore and optimize official ASCII logo (`logo.txt`).